CVE-2026-20940
Published: 13 January 2026
Summary
CVE-2026-20940 is a high-severity Untrusted Pointer Dereference (CWE-822) vulnerability in Microsoft Windows 10 21H2. Its CVSS base score is 7.8 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Privilege Escalation (T1068); ranked at the 10.2th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified are NIST 800-53 SI-16 (Memory Protection) and SI-2 (Flaw Remediation).
Threat & Defense at a Glance
Threat & Defense Details
Mitigating Controls (NIST 800-53 r5)AI
Directly addresses the vulnerability by requiring timely remediation through vendor patches for the heap-based buffer overflow in the Windows Cloud Files Mini Filter Driver.
Implements memory protection mechanisms such as ASLR and DEP to prevent successful exploitation of heap buffer overflows by unauthorized code execution.
Enforces least privilege on local low-privileged accounts, limiting the potential impact and attack surface for privilege escalation attempts via the driver vulnerability.
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Local heap buffer overflow in kernel driver directly enables local privilege escalation via exploitation of vulnerable system component.
NVD Description
Heap-based buffer overflow in Windows Cloud Files Mini Filter Driver allows an authorized attacker to elevate privileges locally.
Deeper analysisAI
CVE-2026-20940 is a heap-based buffer overflow vulnerability in the Windows Cloud Files Mini Filter Driver, published on 2026-01-13T18:16:21.313. The issue, associated with CWE-822, carries a CVSS v3.1 base score of 7.8 (AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H), indicating high severity due to its potential for significant impact on affected systems.
A local attacker with low privileges (PR:L) can exploit this vulnerability through local access (AV:L) with low attack complexity (AC:L) and no user interaction (UI:N). Successful exploitation enables privilege escalation, granting the attacker high-level confidentiality (C:H), integrity (I:H), and availability (A:H) impacts without changing scope (S:U).
The Microsoft Security Response Center advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-20940 details mitigation strategies and available patches for this vulnerability.
Details
- CWE(s)